Acetabular reamers are used in hip replacement surgery to prepare the acetabulum of the hip of a patient before the attachment of an acetabular cup thereto. In such surgeries, there is typically a need to prepare the acetabulum so that a substantially spherical cap-shaped surface is provided to receive a substantially hemispherical acetabular cup. To that effect, a surgeon typically uses a reamer including a substantially hemispherical reaming element in which asperities are formed. The reaming element is longitudinally mounted to the distal end of an axle and the axle is attached to a rotary power tool such as, for example, a drill. The drill rotates the axle about the longitudinal axis of the axle, thereby rotating the reaming element to allow reaming of the acetabulum.
Hip replacement surgery is performed typically after having performed a relatively small incision in a patient, the incision being used for introducing and removing surgical instruments and tissue debris therethrough. Each time an instrument is inserted in the patient, or removed therefrom, there is a risk that soft tissues adjacent the incision become damaged by this action.
In the above-described reaming method, the surgeon typically needs to remove and re-insert repeatedly the acetabular reamer to change the reaming element by a reaming element having a slightly larger diameter in each successive iteration. This allows the surgeon to gradually ream the acetabulum to a desired shape and dimension.
In turn, this requires that many reaming elements be brought into an operating room, which results in relatively large sterilizing costs. Furthermore, the repetitive insertion and removal of the acetabular reamer from the patient is time-consuming and may cause injuries to soft tissues adjacent the incision.
Another problem of many conventional acetabular reamers is that the reaming element typically includes asperities that are spaced apart from each other. These asperities therefore do not produce directly a relatively smooth surface and the surgeon needs to move the acetabular reamer in a substantially ball-joint-like motion inside the patient to achieve a substantially uniform surface suitable for the attachment of the acetabular cup thereto. Since the surgeon typically does not see the result of this operation, there is always a risk that the resulting surface is not smooth enough and results in sub-optimal implementation of the acetabular cup. Another disadvantage of this motion is that, once again, it creates a risk of injuring soft tissues inside the patient.
A few acetabular reamers having variable dimensions have been previously described. For example, U.S. Pat. No. 6,918,914 issued on Jul. 19, 2005 to Bauer describes an acetabular reamer including arcuately-shaped segments that are extendable and retractable about a center point to create variably dimensioned recesses in an acetabular region. However, in this acetabular reamer, when the arcuately-shaped segments are moved away from the central location, the arcuately-shaped segments become spaced apart from each other, which therefore create gaps therebetween. In turn, this requires that the surgeon operate the acetabular reamer substantially in the ball-joint-like motion described hereinabove. Also, when the acetabular reamer is used to ream the acetabulum, mechanical forces transmitted by the arcuately-shaped segments to the remainder of the acetabular reamer are relatively large, which therefore requires that the mechanism used to extend and retract the arcuately-shaped segments be relatively sturdy. This leads to a restriction to a relatively small number of the number of arcuately-shaped segments that can be provided because of size limitations present in such reamers. Also, the surface formed by the arcuately-shaped segments is spherical at only one single overall diameter. For other dimensions, the reamed surface will deviate from a perfect sphere, and since the number of segments is relatively small, such deviations are relatively large in the acetabular reamer proposed by Bauer.
A US Patent Application filed by Termanini and published under the publication number 2006/0217730 on Sep. 28, 2006 describes another acetabular reamer including deployable segments deployable by a deployment mechanism. A disadvantage of this acetabular reamer resides in the presence of pivots in the deployment mechanism, the pivots being load-bearing when the acetabular reamer is in use. Such pivots are relatively fragile and introduce failure points in the design of this acetabular reamer. Also, manufacturing imprecisions in the pivots can lead to the creation of vibrations when the acetabular reamer is in use. Furthermore, the pivots form a structure that is relatively difficult to clean and sterilize.
Another extendable acetabular reaming system has been described by Temeles in U.S. Pat. No. 6,283,971 issued Sep. 4, 2001. In this reamer, a reamer head has a convex forward surface attached to a plate that defines an interior space therebetween. The forward space includes apertures extending therethrough and the base plate includes a central aperture over which a flexible bladder is mounted within the interior space. The reaming system includes cutting blades mounted to the bladder and positioned so as to correspond with respective apertures. The bladder is inflatable so as to extend the blades through the apertures to a variable extent. Once again, in this system, there are gaps between the blades, which will therefore not alleviate one of the problems mentioned hereinabove. Also, any gap between the blades and the apertures will create vibration in the acetabular reamer when the acetabular reamer is used to ream the acetabulum.
Accordingly, there is a need in the industry to provide an improved acetabular reamer. An object of the present invention is therefore to provide such an acetabular reamer.